Of the countless pictures Anthony Browne produced as a child, only a single example survives. "It's from when I was about six," he says, "and it's of a pair of legs - mine, probably - in short trousers. Poking out of one sock is a little figure in a pirate's hat, and - this is slightly embarrassing - there's another one disappearing up the leg of the shorts; all you can see are his feet waving around. And there's a voice bubble coming down from above asking 'What's in my sock? And who's going up my trousers?'"

The legs, he believes, had been subjected to what he and his brother called "the shape game". It's a game that pivots on the act of transformation: one player sketches an object - "a circle, a star, a hat, anything" - the next adds a couple of pencil strokes to set it off in a new direction. "And I imagine what happened was that I drew a pair of legs walking along, then made them over into something different: into a story. I only wish," he laughs, "it were a bit less psychological-seeming. Nothing even vaguely like this happened to me. It's not meant to be dark, just funny!"

Perhaps. But what began as straightforward, if off-beat, humour in his childhood pictures has shifted since then into dicier, more liminal territory: as a children's illustrator, Browne's greatest strength is his willingness to let the darkness in. His work traces a line back through the threat and promise of Jan Pienkowski, Maurice Sendak and, ultimately, Lewis Carroll, marrying surrealist wit with real, honest-to-goodness menace in drawings in which kettles sprout ears, faces scream out of tangled branches and shadows bulge and slide and unpick themselves from their owners. It is the resultant atmosphere of ambiguity - the implication that nothing, not even what's before our eyes, can be relied on - that lends his work such complex and enduring appeal, and that made his appointment as the UK's sixth children's laureate earlier this month such an exciting one. His stories, said the former poet laureate Andrew Motion, "give deep and immediate pleasures ... his work entrances children, and has influenced an entire generation of illustrators."

First dreamed up, so the story goes, by the then-poet laureate Ted Hughes and his friend Michael Morpurgo while the pair were carp-fishing, the children's laureateship carries a two-year tenure and a bursary of £15,000. Browne's first move as laureate, he says, will be to attempt to reinvigorate the role of picture books in society, "to encourage everybody to value the act of looking. In recent years, picture books have become the sole province of the very young; children are encouraged to move on to 'proper' books earlier and earlier. Looking is just as important as words: if vision is marginalised, we lose our ability to really see."

Of Browne's antecedents in the role, only one, Quentin Blake, is an illustrator; like Blake, the others - Morpurgo, Jacqueline Wilson, Michael Rosen, Anne Fine - are all authors with established public profiles. Although his fine watercolours, in which every hair and blade of grass are painstakingly picked out, are instantly recognisable to scores of children, Browne himself is a little-known figure; one of his chief anxieties about the job is the amount of talking it will entail. "Writers are articulate. Artists find it more difficult," he suggests. "For Michael [Rosen, his immediate predecessor] I don't think it was that different from what he did already: broadcasting, speaking, reading ... My life is sitting in a room on my own, painting pictures. So, yes: I'm a little bit nervous about that."

He shouldn't be. In person, Browne turns out to be one of nature's talkers; warm and easy, with a fondness for the demonstrative pronoun ("we moved to this pub", "we went to this school") that leaves you feeling as if you're peering over his shoulder at a shared history. It's a history that began in 1946 in Sheffield where Browne was born, the second son of his parents, Jack and Doris. Shortly after his arrival, the family moved to his grandparents' pub in the small village of Wyke, near Bradford; the pub itself he remembers as "cramped, dark, cold, and pretty rough - working-class men drinking Tetley's bitter, which was known as 'fighting beer'. My dad watered it down, but it didn't stop the fighting."

The son of a Yorkshire farmer, Jack Browne joined up as soon as the second world war broke out - a decision that would cast a long shadow over Browne's childhood. "It was a very traumatic experience for him," Browne says now. "I found his diaries after he died; he wrote about killing German guards with his bare hands - a shocking thing to discover about your gentle, loving father. My mum told me she came into the house one day and found him in a frenzy, wrestling on the floor with a vacuum cleaner: when he came to, he said he'd thought it was a German. There was no post-traumatic stress therapy; the memories hung pretty heavily. Whenever he drew for us it would be of soldiers in uniforms."

Between teaching cadets after the war and moving to the pub, Browne's father was briefly employed as an art teacher ("in a private school, where you didn't need qualifications"), and it was he who first prompted Browne to pick up a pencil. "We learned by copying him," Browne explains. "The first things I remember drawing were battles - big sheets of paper covered in terrible scenes of carnage - though when you looked closely there were little jokes and speech bubbles and odd things going on in the background." Further inspiration came from comics, but in the end, Browne found, drawing "was simply something I did: in the same way that I loved to kick a ball around, I loved to draw".

As he grew older, his hobby began to yield benefits. Browne and his brother attended the local school, where his skill with a pencil provided a shortcut to popularity. "People asked me to draw pictures; the other kids were impressed, though it very nearly got me into trouble on one occasion. We had a very attractive English teacher, Miss Jones, and one lesson, to impress the others, I started drawing her naked - or at least," he grins, "what I imagined her to look like naked. And of course, she discovered me. I was mortified ... but she picked the picture up, smiled and walked away! She said nothing, and I never saw it again."

Browne's school was supportive of his artistic ambitions; however, despite embarking on English and art A-levels, he left without taking the exams. "I was bored," he confesses. "So I left, and did my foundation year at art college in Leeds. And it was in that year that my dad died."

The shattering effect of his father's sudden death on the 17-year-old Browne would play out for years to come in stories haunted by flawed fathers. The father in his chilling, crepuscular retelling of Hansel and Gretel is shamefully weak, dominated by the children's chain-smoking stepmother; in Piggybook he is obnoxious; in Browne's best-known work, Gorilla, he is all absence: cold and distant, glimpsed from behind as he hunches over his desk. And yet when he talks about his own childhood, Browne is full of praise for his father, whom he describes in warm, almost reverent terms. It was many years before he was prepared to recognise, then investigate, the disjunction.

"I slowly became aware that people kept asking: 'Why d'you give dads such a hard time?'" he says. "At first I was defensive, thinking, no, I don't - but of course they were right. And then I started to wonder whether it was to do with my not forgiving my dad for going away when he did."

His recollection of the day itself is quasi-mythical, filled with the sort of symbols and portents that inflect his stories. "It was Easter Monday," he remembers. "I was playing rugby for the first time with the men's team, and my parents had come to watch. My brother was playing, too; I travelled on the coach with the other men; it felt like a real coming-of-age moment. The sun shone, we won, and afterwards we drank in the bar with my parents and all these heroes I'd been watching for years. I felt I was really pleasing my dad, being the kind of son he wanted.

"And then we got home. Dad was mending a plug when suddenly he fell, seemingly in slow motion, and started writhing around making these terrible noises. It went on and on: we didn't know what to do . . . and then he was just lying there: this great, god-like figure on the floor, amid this scene of total devastation. I'd thought he was invincible. And I'd just started to rebel against him; we'd only just begun to argue ..."

For years afterwards, it's possible to read Browne's books as one long answering-back: a means of carrying on the barely begun argument beyond the grave. It wasn't until much later that the chance discovery of his father's old dressing gown allowed Browne to move their relationship beyond that frozen moment. "My mother had come to live with us, and she'd brought this old suitcase. When I opened it, there it was: dad's dressing gown, just as I remembered it. It really took me back to being a small boy, thinking of him as a god who could do everything. The memory freed me to do a positive book about him [the celebratory My Dad]. Though I won't say I'd never criticise fathers again ..."

After graduating from art college, Browne found work as a medical illustrator at Manchester Royal Infirmary, a job he credits with teaching him how to "use watercolours in a controlled, tight way, and tell stories in pictures". From there, he went on to design greetings cards for Gordon Fraser, until eventually, feeling the need to supplement his "fairly meagre" income, he sent off some of his more child-oriented designs to publishers. Hamish Hamilton suggested he try his hand at a picture book, and introduced him to Julia MacRae, who would become his editor for the next 20 years. The idea for the first book they produced together, Through the Magic Mirror (1976) was based on ("stolen from") Magritte's portrait of the man who looks into a mirror and sees the back of his head; it was Browne's first foray into the playful surrealism that permeates his work. "It wasn't a conscious decision," he says now, "but actually, all children are surrealists. It catches an echo of the way they see the world, looking at it for the first time." (His ongoing fascination with Magritte would, years later, land him in hot water. After publishing Willy the Dreamer, in which Willy dreams of becoming a painter, Browne's French publisher called to inform him he was being sued by the Magritte estate. "None of the pictures looked anything like the originals, but his estate paid a very expensive art copyright lawyer to go through the book saying 'This is an infringement, and this, and this'. I thought I was paying homage. It's a peculiar business.")

Several modest successes followed, but it wasn't until the 1983 publication of Gorilla, which won a raft of prizes, including the Kurt Maschler award and the Kate Greenaway medal (which he'd win again in 1992 for Zoo), that his work shot to prominence. "Force me to choose my best book, and I always come back to Gorilla," he admits. "It was the first time I felt I understood what picture books could do." The now-classic story of lonely Hannah whose disappointment on receiving a toy monkey blooms into delight when it swells into a living, breathing gorilla who takes her everywhere (the zoo, a café, dancing in the moonlight) her own father is too busy to take her, took fire from two separate sparks. "The first," Browne explains, "was a childhood birthday. I'd longed for a trumpet, a real one, but when I woke in the night and opened my present, I found this shiny plastic version. I remember the disappointment, vividly. And the second was a little boy in the village I used to live in. His parents had split up, and he was living with his mother. He could only have been about four, but he wandered the village, and practically every day he'd knock on my door, dressed in his Superman outfit. I think he saw me as a father figure, and it made me think about loneliness - the way Hannah looks for a father."

Fathers again. Asked to explain his fascination with gorillas, Browne begins by saying "well, they're glorious to draw, in the way old people's faces are - all the lines", but soon admits "it is to do with my dad, I think. He was a big man, but kindly, and gorillas are like that: powerful, capable of aggression, but mostly gentle, sensitive." It's a view he holds even though his only real-life encounter with gorillas ended badly. "A production company asked me to present a programme on picture books," he recalls, "and they thought it would be a great idea for me to meet my first gorilla. The keepers explained that the gorillas needed to get used to me, so I had two sessions before the cameras showed up, and they'd groomed me, and climbed on my back. But it turned out the zoo-owner, John Aspinall, had had an argument with the TV company about how much they were paying him, so on the day itself, as I was going in, he threw rose petals into the cage. These are like sweets for gorillas; they get very excited. And the first gorilla came up to me and suddenly sank her teeth into my calf. It was the most excruciating pain I've ever felt. I knew I was hurt: the leg of my jeans was turning black. Eventually the producers saw what was going on and took me to hospital."

Although he's never ventured back into a cage, his preoccupation with primates endures. His creation of meek, wistful Willy the chimp, who battles the bully Buster Nose and befriends gentle giant Hugh Jape, proved his ability to tap into the anxieties children wrestle with; he tackled social exclusion and snobbery through the unobtrusively sophisticated layered viewpoints of Voices in the Park (another Maschler winner), and the sexual division of labour in Piggybook. In 2000 he became the first British illustrator to win the Hans Christian Andersen award (illustration's highest accolade) for a body of work that consistently, distinctively blends sunshine with shadow, and tackles tricky subjects with warmth and wit. "Children are more than capable of coping with all kinds of stories; it's adults who are threatened by the darkness in children's books," he says. "But it has a place: an essential place. If we insist on telling children that everything in the garden is lovely, we're doing them a disservice."

Browne on Browne

I see Hansel and Gretel as a breakthrough book for me, and one of the reasons is because I started to apply meaning to the hidden details. Whereas in previous books I had treated them as little more than doodles in the background, in Hansel and Gretel I employed them as subtle aids in telling the story. Not only do they re-enforce the main narrative: they also offer an insight into extra narrative information that isn't expressed in the text.

Here, as the stepmother prepares to wake the children, we can see that her shadow on the wall behind her is extended by the gap in the curtains so that it appears as if she is wearing a pointed hat. As she formulates her plan, the implied hat links and equates her with the witch whom the children encounter later in the story. If you look even more carefully, you can see this triangular motif is repeated several times within the picture: the shadow above the chest of drawers, the steeple of the church in the picture on the wall, the mouse-hole in the skirting board and an ambiguous object on top of the wardrobe.